1. Field of the Invention
This disclosure relates to an improved method and apparatus for practicing the method of extracting water from wet gas to provide, at the outlet, a flow of gas substantially free of water. The invention is particularly applicable to the processing of natural gas in which the gas has entrained in it water of sufficient quantity to make its further transportation and storage difficult and includes improved means of extracting the water from the gas at a point adjacent the area where the gas is collected to provide, at the outlet, gas substantially free of water so that it may be more economically and efficiently transported, stored, processed, and used.
The field of the invention is particularly concerned with a well-known method for extracting water from gas known as "glycol dehydration" or liquid desiccant dehydration" in which the wet gas is mixed and/or contacted with glycol or some other liquid desiccant, the glycol absorbing water from the gas, the glycol then being heated to evaporate the water from it, and the anhydrous glycol being recirculated for adsorption and/or admixture with wet gas, in a continuous process. The invention improves the known techniques of glycol dehydration by providing a method in which the gas is more intimately contacted with the glycol for more improved extraction of water from the gas and includes improved apparatus wherein effective water extraction can be achieved with vessels of reduced height and better economy of construction.
2. Description of the Prior Art
The invention, as above mentioned, is concerned with extracting water from wet gas and is particularly applicable for utilization in the petroleum processing industry wherein natural gas commonly has entrained in it a quantity of water. If the water remains in the gas as it is transported, stored and used, it is a source of many problems. The water entrained in the gas easily freezes and thereby can plug pipelines, valves, orifices, etc. In addition, the water constitutes a non-combustible portion of natural gas as it emanates from production sources, and the handling and transportation of this portion of the naturally occurring gas stream is uneconomical and inefficient. For these and many other reasons, it is highly desirable that as much water as possible be extracted from natural gas after it flows from gas production sources, and the extraction process is preferably carried out in the vicinity of the source where the gas is produced. In this way the gas can be processed to remove excess water before it is conveyed to transmission lines or is further processed.
There are a variety of ways for separating water from gas, but the method most commonly employed in the petroleum industry is the use of glycol or other liquid desiccant dehydrators. Glycol readily mixes with water and has a lower vapor pressure than water. Thus, it is well known to pass wet gas into contact with glycol wherein the water in the gas is absorbed by the glycol. The gas is then passed in an upward column wherein the glycol/water mixture physically separates from the gas stream. The glycol/water mixture is then heated to drive off the water, the dry or anhydrous glycol then being recirculated to contact wet gas in a continuous process so that water is extracted from a gas stream.
A difficulty associated with most glycol dehydrators is that in order to achieve sufficient contact of wet gas and glycol, it has been necessary to construct vessels of relatively tall vertical height. The typical absorber vessel includes a plurality of vertical trays with a series of bubble caps in each tray. Glycol is maintained on each tray at a shallow depth, the gas passing through the bubble caps where it contacts the glycol. A certain minimum spacing is required between the bubble trays in order to allow entrained droplets of glycol carried by the upwardly moving gas stream to fall downwardly. It is apparent that constructing vessels of high vertical height is relatively expensive and, in addition, such construction requires that the vessels be transported to the site in a horizontal position and subsequently erected in place. With the current commonly practiced techniques of glycol dehydration, it is not practical to fabricate a complete gas dehydration system in a factory and transport it for direct installation in the field because of the vertical height requirements.
The present invention provides a means of utilizing glycol gas dehydration in a manner which provides improved effectiveness and efficiency in contacting wet gas with glycol and in a manner which does not require tall vertical vessels having a plurality of bubble trays. The present invention provides improved means of glycol dehydration utilizing shorter height vessels and in an arrangement wherein the percentage of entrained water removed from wet gas is significantly improved.
The present invention, in which this disclosure is a continuation, achieves the results and benefits above described while employing vessels which are more economical of construction and in which improved flow characteristics are achieved.